The invention relates to a method for preventing or minimizing operational failures in a technical installation. At least one criterion is defined by means of influence quantities that are accessible to a control system. In particular, these influence quantities are monitored installation quantities and/or other influences. More specifically, the other influences are, e.g., external influences. The presence of that criterion is used to forecast an impending operational impairment and/or an impending failure of one or more parts of the installation. This criterion is constantly monitored at short time intervals in order to generate a forecast of the expected failure probability and/or the operational impairment. The forecast is used, if necessary, to take or prompt early countermeasures to prevent the failure and/or the operational impairment. The forecast is also used, if necessary to take steps for minimizing the effects of the impending failure and/or the operational impairment. The criterion used for the forecast is derived from the respective installation quantities in such a way that irregularities are detected at a time when none of the installation quantities have exceeded a limit that would require the immediate shutdown of the installation or a part thereof.
Humans continue to learn to control and profitably use increasingly complex technical processes. This is made possible, in particular, by the wide use of automated controls, which assume highly complex open-loop and closed-loop tasks in normal operation. However, with the increasing complexity of technical installations, the failure probability of the technical installations also increases, since the failure probabilities of the relevant installation components are additively superimposed. The failure probability of the entire installation thus increases with the number of its relevant components. Despite this increasingly serious problem of limited availability of complex installations, an effective solution to this problem has thus far not been proposed. The shortening of maintenance intervals has its limits because of the increased downtimes required to carry out the maintenance. Commercially available diagnostic programs, which are used to quickly localize errors or malfunctions in an installation, can be activated only after an error or malfunction has occurred, i.e., when the installation may already be down. In other words, the error or malfunction is dealt with only after it has occurred, which is an outcome of the worldwide causality principle. Even the latest diagnostic programs cannot prevent long downtimes because the rapid repair required in the case of an acute failure depends on completely different factors, such as the availability of special replacement parts.
German Laid Open Publication DE 40 08 560 A1 discloses a method for determining the remaining life of a unit that is composed of a plurality of components and that has at least one function. The calculations are performed, for example, to determine whether inspection or maintenance measures can be delayed by one or more years. An expert system is used for these calculations, which includes an information acquisition support device, an inference device, a user interface, an external interface and an information bank. Thus, this is a very complex method with respect to the required hardware, especially if a very large amount of information is to be recorded and processed, so that the information acquisition support device becomes very large.
EP 0 509 817 A1 has a similar disclosure, except that only the remaining life of a cutting tool needs to be determined, and the size of the expert system, in particular the number of sensors required by the expert system, is thus kept within limits.
EP 0 908 805 A1 teaches a more or less complex device for pre-emptive maintenance purposes. Furthermore, this device becomes active only at one-hour intervals in order to check whether maintenance is due by means of average values of the data stored, respectively, during the past hour. This may be sufficient for conventional maintenance intervals of e.g., one or several years so as to detect wear-related aging processes. In practice, however, one finds that acute problems occur too, which are caused, for example, by incorrect operation or the like. There, such a slow response is not sufficient to avert major damage.
EP 0 626 697 A1 relates to a plant monitoring and diagnosing method and a plant equipped therewith. As shown in FIG. 7 and FIG. 11 of EP 0 626 697 A1, the diagnostic system is coupled with the control system. The data flow, however, is directed only from the diagnostic system to the control system, so that the diagnostic system requires its own hardware, including its own sensors and/or evaluation circuits for sensor signals, which is comparatively expensive.
Finally, EP 0 612 039 A2 teaches a maintenance system that takes the wear of components in a plant into account. The method disclosed therein includes determining, as precisely as possible, the expected life of individual components of a plant, taking into account the concrete operation conditions. The introduction of this reference shows, however, that this reference focuses on developing and designing new, low-maintenance plants. Insofar, the system presented is not executed in real time and can therefore not be used to monitor a finished plant. Such a system includes a memory and computation and display means and can be connected to a monitoring system of a specific plant. This makes it possible to optimize the computations. However, here too, the system requires its own hardware, which makes its use uneconomical in many cases.